A great deal of respect and authority is automatically assigned to one identified as a lawyer. You likely assume that such an individual has a vast knowledge of all legal matters pertaining to the particular branch of law that they claim to specialize in. Yet there are legal aspects of certain fields that even a lawyer working in that field may not be familiar with. These may be accepted industry standards or regulatory compliance issues that only one practicing in such field would know. For this reason, you often see attorneys who also hold additional professional licenses. For example, a lawyer practicing real estate law may also obtain a realtor's license, while an attorney specializing in tax law may also become a certified public accountant.
You may think that you have hit the veritable jackpot if you are able to find such an attorney to represent you. Yet just as you would want to research an attorney's legal background before seeking their services, so too should you check into their professional licensure. As has been detailed in this blog in the past, attorneys are somewhat limited in the ways they can solicit their services. Thus, advertising a dual specialist would certainly help them in securing new clients.
Claims of additional professional specialties, however, cannot be made based on experience in an area alone. Rather, the American Bar Association's Model Rules of Professional Conduct state that in order for an attorney to advertise themselves as a professional specialist, they must be certified through a state-approved accrediting organization (or one approved by the ABA). The name of that certifying organization must also be clearly certified in any communications it makes with you for the purpose of soliciting their services.